A Radical Correction for Inter Fragment Interaction Energy (IFIE) between Fragments Sharing Bond Detached Atom (BDA)

Abstract

Recently, the fragment molecular orbital (FMO) method has attracted considerable attention as an electronic structure calculation scheme applicable to macromolecular systems. As a major advantage, the lists of inter fragment interaction energies (IFIEs) are straightforwardly obtained from the FMO calculations. It has been well recognized that the IFIE-based analyses are useful to grasp the nature of interactions in the given target system in practical applications. However, there exists a severe limitation that the values of IFIE between covalently bonded fragments takes an abnormally large value (about -15.2 hartree) due to the fragmentation at the so-called bond detached atom technique, and this should degrade the usability of FMO calculations in several cases. In our pervious paper (J. Comput. Aided Chem. 18, 143 (2017)), we examined a correction method to solve this problem, based on the fictitious dissociation processes. In this paper, we propose a more realistic model with radical dissociation correction scheme.